RESPONSES OF SUBJECTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE AFTER EXPOSURES TO 0.3 PPM OZONE

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Abstract
The respiratory mechanics of intermittently exercising persons with chronic obstructive pulmonary disease (COPD) were unaffected by a 2-h exposure to 0.2 ppm O3. Employing a single-blind, cross-over design protocol, 13 white men with nonreversible COPD (9 current smokers; mean FEV1/FVC, [forced expiratory volume/forced vital capacity], 56%) were randomly exposed on 2 consecutive days for 2 h to air and 0.3 ppm O3. During exposures, subjects exercised (minute ventilation, 26.4 .+-. 3.0 l/min) for 7.5 min every 30 min; ventilation and gas exchange measured during exercise showed no difference between exposure days. Pulmonary function tests (spirometry, body plethysmography) obtained before and after exposures were unchanged on the air day. On the O3 day the mean airway resistance and specific airway resistance showed the largest (25 and 22%) changes (P = 0.086 and 0.058, respectively). Arterial O2 saturation (SaO2) obtained in 8 subjects during the last exercise interval showed a mean decrement of 0.95% on the O3 exposure day; this change did not attain significant (P = 0.074). Nevertheless, arterial O2 desaturation may be a true consequence of low-level O3 exposure in this compromised patient group. As normal subjects undergoing exposures to O3 with slightly higher exercise intensities show a threshold for changes in their respiratory mechanics at .apprx. 0.3 ppm, persons with COPD are apparently not unduly sensitive to the effects of low-level O3 exposure.

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